Pacing and Defibrillation: Clinically Relevant Basics for Practice

Understanding cardiac pacing requires an intimate consideration of two key elements: stimulation threshold and sensingThe chronaxie is important in the clinical practice of pacing because it approximates the point of minimum threshold energy required for myocardial depolarizationOne can specifically consider the situation of postdefibrillation pacing, when stimulation thresholds may be increased due to tissue ischemia during the preceding tachyarrhythmia or at the time of defibrillationCertain drugs used in patients with cardiac disease may also increase pacing thresholdsNewer pacemakers and implantable cardioverter-defibrillators that can support higher current drains for capacitor charging and high-rate antitachycardia pacing use lithium–silver oxide–vanadium chemistriesIn unipolar pacing systems, the lead tip functions as the cathode and the pulse generator as the anodeIn bipolar systems, the lead tip serves as the cathode and a lead ring acts as the anode.